Radiopharmacist's Notes · Dose Calibrator QA Sources

Daily · monthly · annual — three QA bands, two owners.

A working dose-calibrator QA programme has three cadence bands and one handoff. The radiopharmacist runs daily constancy and monthly multi-isotope checks; the physicist runs the annual accuracy + linearity protocol. The same four-isotope reference set anchors all three. This post draws the bands and the handoff.

The three cadence bands

Tests, thresholds and what the log entry looks like

Band	Trigger	Test	Pass	Fail	Log
Daily — radiopharmacist	Before first dose dispensed; after warm-up	Constancy reading on one long-lived reference (typical: Cs-137 or Co-57)	Δ within ± 5 % of decay-corrected expected activity	HOLD dispensing. Re-read after 5 min; if persistent, escalate to physicist	Signed constancy log entry; trend chart updated
Monthly — radiopharmacist	First working day of the month	Constancy reading on the full four-isotope set across the energy span	Δ within ± 5 % at every isotope; no consistent direction of drift across the month	Document and flag for the physicist annual-review file	Monthly QA log entry; cross-check against daily trending
Annual — physicist	Once per calendar year; before AERB inspection	Full accuracy + linearity protocol using the four-isotope set	Accuracy Δ within ± 10 %; linearity deviation ≤ 5 % across the clinical activity range	Quarantine dose calibrator until service / re-calibration; re-test before return-to-service	Annual QA dossier entry; result is one of the AERB inspection inputs

Source: AAPM TG-181 PET / Nuclear Medicine QA; AERB Safety Code for Nuclear Medicine Facility (Section on dose-calibrator QA).

The handoff

Daily / monthly feeds annual

The radiopharmacist owns daily and monthly. The physicist owns annual. The handoff is the monthly log + the trend chart — the physicist arrives for the annual already knowing the year-shaped drift pattern.
The same reference set is used by both. The annual physicist accuracy / linearity reading is on the same sources the radiopharmacist reads every morning — the chain of evidence is unbroken from daily through annual.
The physicist signs the annual dossier; the dossier goes into the AERB inspection file. The radiopharmacist signs the daily and monthly logs; those logs are the evidence the dossier rests on.

Replacement cycle

When each isotope in the set needs replacing

Co-57 (T½ 272 d): replace annually, typically paired with the Co-57 flood-source replacement cycle. New source arrives ahead of old source's end-of-useful-life so the trending log spans the changeover.
Cs-137, Ba-133, Co-60: multi-year service life. Replace when the source-to-background signal degrades below useful counting precision — typically every 5–10 years depending on initial activity and clinical activity range needed.
Saxsons supplies the replacement source with calibration date aligned to the planned in-service date. The old source enters decay store and returns through the Source Return Service. AERB inventory updates on receipt of the disposal certificate.

Source: NNDC ENSDF half-life data; AAPM TG-181 source-replacement guidance.